1. Field of the Invention
The present invention relates to an electrostatic recording apparatus. More specifically, the present invention relates to an electrostatic recording apparatus which employs a photosensitive member composed of amorphous silicon.
2. Description of the Prior Art
For example, in the U.S. Pat. No. 4,460,669 issued on July 17, 1984, a photosensitive member using amorphous silicon is disclosed and this photosensitive member comprises a bulk layer of amorphous silicon formed on a support. Oxygen, carbon or nitrogen is doped in this bulk layer together with an element or atom belonging to the group III of the periodic table such as boron. Then, the uppermost layer region, that is, the surface layer region of the bulk layer is formed as a so-called non-doped layer wherein any of oxygen, carbon and nitrogen and any of elements in the group III is not doped.
The photosensitive member disclosed in this U.S. Pat. No. 4,460,669 is, presumed to improve the charging property. This is because the surface layer region, that is, the non-doped layer region is formed in the bulk layer, so carrier traps are not generated which are generated in the vicinity of the surface of the conventional photosensitive member having no non-doped layer and therefore the charing property will be improved.
On the other hand, in the electrostatic recording apparatus, generally light is irradiated to expose the photosensitive member and to eliminate the residual charges of the photosensitive member. For light sources for these purposes, for example, halogen lamps or the like are utilized. The halogen lamp has a wide range of luminous spectrum and the peak wave length is about more than 700 nm. Even if the improved photosensitive member disclosed in the U.S. Pat. No. 4,460,669 as cited previously is employed, when such a light source having the same range of wavelengths as that of the conventional one is used, light from this light source is transmitted through the surface layer of the photosensitive member and plunges into the bulk layer, and a large number of carriers are produced in the bulk layer likewise the convention cases, and the carriers are caught in traps. This means that even if the photosensitive member is employed wherein the non-doped layer is formed on the surface of the bulk layer, when light sources for exposure and discharge of long wavelengths like the conventional ones are used, resultingly, a sufficient improvement in the charging property is not achieved.